Study of the radiolytic degradation of Zectran in water by LC-MS/MS

Intensive agriculture requires the use of several phytosanitary products. Pesticides of the carbamate family are used to eliminate the crop pests by acting on their nervous system. This study aims to determine the kinetic degradation of Zectran, the 4-(dimethylamino)-3,5-dimethylphenyl N-methylcarbamate (20 mg L−1) using 60Co gamma radiation source. The absorbed doses were analyzed by Liquid Chromatography (LC-DAD) using a column RP-18 PRISM (250 mm × 4,6 mm, 5 µm) and a mobile phase composed with a mixture of acetonitrile and water (70/30). The results showed that the Zectran was completely eliminated at absorbed dose of 6 kGy. The pseudo-first kinetic order could describe the removal of Zectran by gamma radiation with kobs = 0.389 kGy−1. The degradation mechanism by gamma irradiation was proposed based on the analysis of the by-products using an LC coupled to a QTOF mass spectrometer. The kinetic rates of the two intermediate compounds were calculated.